In ‘H-bridge’ circuits, protective measures are implemented against currents having an excessively high magnitude, termed ‘overcurrents’, for each of the power transistors.
When a transistor detects a high stress phenomenon, termed ‘overstress’, all of the transistors are turned off at the same time.
FIG. 2 illustrates a system according to the prior art. It is seen in FIG. 2 that, in the event of detection of a current having an excessively high magnitude, termed ‘overcurrent’, all of the transistors are turned off at the same time.
In the case of an inductive load, this involves a phase of discharging through a freewheeling diode to ground and to the positive power supply.
The inductive discharge phase in the freewheeling diodes brings about a substrate injection into the electronic circuits and means that expensive semiconductor processes have to be implemented to resist this.
The inductive discharge phase in the freewheeling diodes also brings about, on the ‘high side’ (that is to say on the side linked to the supply voltage), an increase in the supply voltage. This means that the decoupling capacitances, and therefore the cost, have to be increased.